1,3-Propanediol (PDO) is a potentially attractive comonomer for a polyester, poly (1,3-propyl terephthalate) (PPT) which is particularly valuable as a superior carpet fiber. There is also commercial interest in the glycol as a multiple functional small molecule.
Typical of these applications is as a monomeric component for polyurethanes, and as a component in many cyclic compounds. Many methods have already been suggested for the synthesis of PDO, including synthesis from ethylene oxide and carbon monoxide catalyzed by rhodium and a co-catalyst and by the hydration of acrolein and hydrogenation of the resulting 3-hydroxypropanal. Acrolein is a readily available reactive organic compound.
U.S. Pat. No. 2,434,110 discloses that acrolein can be hydrated in the presence of an acidic catalyst to form 3-hydroxypropanal (HPA). The reaction preferably takes place at an elevated temperature using 5-30 wt. % solution of acrolein in water and an acid, as for example, sulfuric acid, phosphoric acid, or the acid salts of these acids as the catalyst. The reaction mixture obtained during the hydration is then hydrogenated in the presence of an active hydrogenation catalyst, as for example Raney nickel. A disadvantage of the process described is the low yield of HPA attributable to the condensation reactions which occur concurrently to the hydration.
U.S. Pat. No. 3,536,763 describes the hydration reaction as being carried out in the presence of a weakly acidic cation exchange resin the functional groups being carboxylic acids. The reaction occurred at from 40.degree.-120.degree. C. Preferably about 0.1 to about 5% of the carboxyl groups are present in the form of the alkali carboxylate, alkaline earth carboxylate, or earth metal carboxylate.
Recent patent activity demonstrates that there is still considerable interest in improving the traditional methods of the manufacture of PDO. One of these improvements has been disclosed in U.S. Pat. Nos. 4,873,378, 4,873,379, and 4,935,554 which disclose methods to produce PDO in one step by ethylene oxide carbonylation using a rhodium catalyst.
Degussa, in U.S. Pat. No. 5,015,789, describes the acrolein hydration/hydrogenation route to PDO using an acidic cation exchange resin containing phosphonic acid groups in the acid or salt form as a catalyst to cause the hydration of acrolein and separation of the catalyst and unreacted acrolein. This is followed by a conventional hydrogenation reaction of the HPA.